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Publication numberUS4197375 A
Publication typeGrant
Application numberUS 05/968,886
Publication dateApr 8, 1980
Filing dateDec 13, 1978
Priority dateDec 12, 1977
Publication number05968886, 968886, US 4197375 A, US 4197375A, US-A-4197375, US4197375 A, US4197375A
InventorsRichard C. Fox
Original AssigneeChevron Research Company
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Photodegradability of plastic polyolefins
US 4197375 A
Abstract
Plastic polyolefins which are resistant to photodegradation are combined with polyisobutylene to improve photodegradability.
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Claims(5)
I claim:
1. A method for improving photodegradability of plastic polyolefin compositions which comprises physically contacting plastic polyolefin compositions which are resistant to photodegradation with a minor proportion of polyisobutylene sufficient to accelerate the photodegradation of the plastic polyolefin, said polyisobutylene having a number average molecular weight of from about 400 to about 900.
2. A method according to claim 1 wherein the polyisobutylene has a number average molecular weight of from about 400 to about 700.
3. A method according to claim 1 wherein the polyolefin is polyethylene.
4. A method according to claim 3 wherein the polyisobutylene is applied to the surface of the plastic polyethylene by dipping said polyethylene into a hydrocarbon solution of the polyisobutylene.
5. A method according to claim 4 wherein the polyisobutylene is present on the surface of the plastic polyolefin in an amount from about 1 to 3 percent by weight based on the polyethylene.
Description
CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation-in-part of application Ser. No. 859,776, filed Dec. 12, 1977 now abandoned.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to photodegradable plastic polyolefin. More particularly, the invention relates to plastic polyolefin containing polyisobutylene as photosensitizer.

2. Description of the Prior Art

Plastic polyolefins are widely used in the manufacture of many articles. Such articles of importance include disposable containers for food and drinks and the like and films for agricultural mulching.

The plastic polyolefins usually degrade to some degree in the sunlight. This degradation is undesirable with articles of manufacture where durability is important, as in the case of artificial turf for playing fields. Various inhibitors, such as the UV radiation absorbing agents, have been added to inhibit photodegradation. See, for instance, U.S. Pat. No. 3,429,841 describing the addition of 2-hydroxybenzophenone and oxidized polymeric wax to propylene polymer fibers as ultraviolet light absorbers.

However, in the case of plastic polyolefins for disposable containers and agricultural mulching films and the like it is ecologically desirable to get rid of the used containers and mulching film. Photosensitizers have been added to the plastic polyolefins to accelerate degradation on exposure to sunlight, thereby facilitating the disposal of the plastic polyolefin articles. See, for instance, U.S. Pat. No. 4,038,227 describing the use of benzophenone and other additives to promote the degradation of polyolefins and U.S. Pat. No. 3,679,777 describing the use of gamma-pyrone ring-containing compound to accelerate the photodegradability of polyolefins.

Pigments have been incorporated into plastic polyolefins, particularly with the use of dispersants such as mineral oil, polyethylene glycol, dioctylphthalate, polyisobutylene, or butyl stearate. See, for instance, U.S. Pat. No. 3,523,916 describing the admixing of pigments and polyolefin with butyl stearate or low molecular weight liquid polyisobutylene in amounts of from about 0.1 to 0.6 weight percent.

SUMMARY OF THE INVENTION

In accordance with the present invention there is provided a method for improving photodegradability of plastic polyolefin compositions which comprises physically contacting plastic polyolefin compositions which are resistant to photodegradation with a minor proportion of polyisobutylene sufficient to accelerate the photodegradation of the plastic polyolefin, said polyisobutylene having a number average molecular weight of from about 400 to about 900, preferably about 400 to about 700.

The improved plastic polyolefin compositions of the invention and articles thereof degrade upon exposure to sunlight over a determinable period of time, as desired, thereby facilitating their disposal.

DETAILED DESCRIPTION OF THE INVENTION

The plastic polyolefins of the compositions according to the present invention are well known for their use in the molding and casting of articles such as containers and films. Included are high and low density polyethylene, polypropylene, poly-1-butene, polystyrene, and ethylene copolymers, mixtures of polyethylene and polypropylene, as well as mixtures of the aforementioned polyolefins, and the like. Such polyolefins are normally solid.

The plastic polyolefin and polyisobutylene are brought into physical contact and combined in various ways. The plastic polyolefin is conveniently melted and mixed with the polyisobutylene with the aid of a conventional mixer of the Banbury type. The polyisobutylene is also readily added to the plastic polyolefin during other manufacturing operations as, for example, in the use of screw extruders.

A preferred aspect of the improved photodegradable plastic polyolefin compositions of the invention resides in the fact that the polyisobutylene photosensitizer may be applied in the appropriate amounts to the surface of the article of manufacture. The polyisobutylene penetrates the surface and provides the desired degree of photodegradability. For convenience of application, the polyisobutylene photosensitizer may be dissolved in conventional solvents such as petroleum hydrocarbon thinner. Preferably, such solvents evaporate at about room temperature and leave little or no residue other than the polyisobutylene.

The improved plastic polyolefin compositions in accordance with the invention may contain other conventional additives. Included are pigments, antioxidants, plasticizers, etc. Other photosensitizers are also included, such as the benzophenones.

The polyisobutylene photosensitizer is readily characterized by its number average molecular weight, as mentioned above. Such polyisobutylenes are normally liquid and are commonly produced by catalytic polymerization of an isobutylene-rich stream. The preferred polyisobutylenes are also characterized by their viscosities, which range from about 500 to 6,000 SSU at 100 F. and from about 60 to 300 SSU at 210 F. The polyisobutylenes are sold by Chevron Chemical Company as Chevron Polybutenes and are designated according to their "Polybutene Grade" as shown in the following table:

                                  TABLE I__________________________________________________________________________            Polybutene (PB) GradePhysical Properties     Test Method            6  8  12 16 18 22  24  32  122 128__________________________________________________________________________Number AverageMolecular WeightMechro Osmometer     SM-180-6            330               440                    530                       640                          730                             800                                 950                                    1,400                                        2,500                                            2,700Viscosity @     ASTM D-445100 F., SSU     & D-446            134               560                  3,400                     5,700                        9,500                           16,500                               40,000                                   123,000                                       715,000                                           890,000Viscosity @     ASTM D-445210 F., SSU     & D-446             41                63                    163                       250                          350                             550                                1,050                                    2,990                                        15,800                                            19,500__________________________________________________________________________

For present purposes the polyisobutylenes having a number average molecular weight of from about 400 to about 900 are most preferred since they provide a desired degree of photodegradability of polyethylene, a preferred embodiment of the invention.

The polyisobutylenes as well as other additives are combined with the plastic polyolefins in the compositions of the invention in any amounts sufficient to accelerate the photodegradation of the polyolefin and provide the desired amount of decomposition along with other physical characteristics. Ordinarily from about 1 to 3% by weight of the polyisobutylene is used based on the plastic polyolefin.

EXAMPLES

The photodegradable plastic polyolefin compositions of the invention are illustrated by the following examples. In these examples a 2-mil commercial polyethylene film was treated with solutions of the additives in petroleum hydrocarbon thinner. After the thinner evaporated, the film was stored inside at 100 F. for 30 days to allow the additives to diffuse into the film prior to outdoor exposure. The 5% solutions provide about 1% by weight of polyisobutylene in the plastic polyolefin. The degradability of the treated polyolefin was evaluated by testing for elongation using an Instron machine in accordance with the general test method outlined in ASTM D-882. The results of the various examples are summarized in the following table:

                                  TABLE II__________________________________________________________________________ELONGATION OF TREATED 2 MILPOLYETHYLENE FILMS           Maximum Elongation of Treated Film, %                     Stored Stored                     Inside Inside                     30 Days at                            30 Days at                Stored                     100 F. and                            100 F. and                Inside                     120 Days at                            ExposedExample         Freshly                30 Days                     Room   OutsideNo.  Treatment1           Prepared                at 100 F.                     Temperature                            120 Days2__________________________________________________________________________1    None       385  420  300    235,                               1602    Hydrocarbon Paint Thinner   365  395  495    200,                               1503    Benzophenone (1%)           365  355  505    10,                               154    PB-8 (5%)  385  390  410    10,                               205    PB-8 (5%) +           375  335  425    10,                               10 Benzophenone (1%)6    PB-16 (5%) 410  375  350    20,                               157    PB-16 (5%) +           345  355  480    25,                               15 Benzophenone (1%)8    PB-32 (5%) 375  360  460    20,                               159    PB-32 (5%) +           355  390  525    80,                               20 Benzophenone (1%)10   PB-128 (5%)           330  305  480    40,                               4511   PB-128 (5%) +           330  395  515    20,                               15 Benzophenone (1%)12   Corn Oil 23           395  350  465    60,                               56 (5%)13   Corn Oil 23           360  300  430    10,                               15 (5%) + Benzo- phenone (1%)14   Corn Oil (5%)           385  330  505    65,                               4015   Corn Oil (5%)           375  365  495    10,                               10 + Benzophenone (1%)16   α-Olefin C8 -C9           385  410  435    195,                               220 (5%)17   α-Olefin C8 -C9           290  375  540    10,                               15 (5%) + Benzo- phenone (1%)18   α-Olefin C13 -C14           385  405  450    135,                               105 (5%)19   α-Olefin C13 -C14           370  390  375    10,                               55 (5%) + Benzo- phenone (1%)20   α-Olefin C15 -C20           280  375  482    25,                               80 (5%)21   α-Olefin C15 -C20           250  435  460    15,                               10 (5%) + Benzo- phenone (1%)__________________________________________________________________________ 1 The number in parentheses after the additive is its concentration in the hydrocarbon paint thinner solution used to treat the film. 2 Duplicate samples.

The above test results show that the low molecular weight polyisobutylenes were particularly effective as indicated by the experiments using PB-8 and PB-16.

While the character of this invention has been described in detail with numerous examples, this has been done by way of illustration only and without limitation of the invention. It will be apparent to those skilled in the art that modifications and variations of the illustrative examples may be made in the practice of the invention within the scope of the following claims.

Patent Citations
Cited PatentFiling datePublication dateApplicantTitle
US3523916 *Jan 26, 1967Aug 11, 1970Phillips Petroleum CoAdditive dispersant
US3797690 *Dec 8, 1971Mar 19, 1974Owens Illinois IncPreparation of degradable polymeric material
Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US4571329 *Aug 13, 1984Feb 18, 1986Babcock-Hitachi Kabushiki KaishaAmmonia reduction-denitration process and apparatus therefor
US5145732 *Feb 26, 1990Sep 8, 1992Osaka Gas Company LimitedHigh bulk density carbon fiber felt and thermal insulator
US5204174 *May 4, 1990Apr 20, 1993Kimberly-Clark CorporationBlends of propylene and butylene homo- and copolymers
US7638090Apr 25, 2006Dec 29, 2009Searete LlcSurveying one or more areas and transmitting one or more signals to one or more sterilization units in response
US7754156Oct 20, 2006Jul 13, 2010The Invention Science Fund I, Llcmedical equipment production
US8114342Apr 28, 2006Feb 14, 2012The Invention Science Fund I, LlcMethods and systems for monitoring sterilization status
US8178042Oct 20, 2006May 15, 2012The Invention Science Fund I, LlcMethods and systems for monitoring sterilization status
US8277724Mar 31, 2006Oct 2, 2012The Invention Science Fund I, LlcSterilization methods and systems
US8758679May 20, 2010Jun 24, 2014The Invention Science Fund I, LlcSurveying sterilizer methods and systems
Classifications
U.S. Classification523/125, 427/336, 524/585, 260/DIG.43, 427/393.5, 524/490
International ClassificationC08L23/02
Cooperative ClassificationC08L23/06, C08L23/02, Y10S260/43
European ClassificationC08L23/02, C08L23/06